Skill Creation in the Fantasy World - Chapter 62: Solo in the Underworld.

After breaking up with his girlfriend, he accidentally acquired a genius system and rose from there against the heavens, becoming invincible..

- Description from Novelupdates

Reborn in the Naruto world, Shin Uzumaki finds himself in the doomed Land of Whirlpools. As a member of the Uzumaki Clan! Trapped in a world filled with war, betrayal, and unimaginable power, Shin’s survival seems impossible.. Until it isn’t!![Ding! Replication System Activated!][Daily Login Reward: Common Replication Card.]​​​​​​​[Newbie Gift: Perfect Sage Body—​​​​​​​Adamantine Sealing Chains​​​​​​​—​​​​​​​​​​​​​​Four Symbols Seal​​​​​​​]With the power to Copy any Ability—whether it’s the Kekkei Genkai or Rinnegan or Forbidden jutsu—Shin begins his journey to dominate the Ninja World. [First task: Save Kushina and prevent the destruction of the Uzumaki Clan.]

WARNING!!!(This novel is R18, The MC steal girls and his abilities on improve with sex alone, less adventure, more sex and humor)The Adventure and His fighting abilities only starts by chapter 10.so enjoythe MC steal girls and more, nobody is fucking his women just a big cock guy fucking everyone's women...NTR, CUCKOLD,LOLI,MILF, HUMILIATION,FEMDOM, MALEDOM AND HAREM .... For real no capI wonder who this body belonged to originally and what happened to the poor bastard's consciousness when I took over. Is he floating around in my body back on Earth, just as confused as I am?I sit on the edge of the bed, trying to make sense of it all.One moment I was on my couch scrolling through my phone, the next I was standing naked in Lady Vivienne's bathroom. No warning, no magical portal, no summoning ritual. Just... poof.

One day, I woke up only find out that I’d become a Demon Lord, an individual responsible for protecting a dungeon. The world I’d been spirited away to was one filled with violence. Gigantic monsters wandered through it and competed with each other each and every day for the right to survive. I had no choice but to strengthen my dungeon’s defenses in hopes of living another day—or at least that was what I’d thought. For some odd reason, I instead ended up spending my days in relaxation and bliss.